有鑒於前人利用參數系統識別法，建立土層系統的模型結構，分析羅東與菁寮兩測站之井下陣列記錄資料，求得整筆地震資料的系統相關參數平均值。但是從許多室內實驗結果得知，土壤參數在震動過程中並不一定為定值。故本研究之目的，在於了解土壤動態參數隨時間改變的趨勢。藉由多模型自適性遺忘因子法則，簡稱AFMM法，將地震資料的時變、非時變區劃分出來後，個別以時變、非時變模型進行識別，主要觀察時變區參數的變化趨勢。此外，還以前人所使用之參數系統識別法分析室內振動台試驗。
　　分析結果顯示，AFMM法能減少時變模型在系統前期的試誤情況，有效截取時變區段以利時變分析，土層之基本共振頻率，在經過主震區某個門檻應變後有頻率降低的現象，事件本身的基本共振頻率亦與地震強度有關。與前人不分區結果比較，不分區結果在阻尼比有低估的情形，頻率部分則可能高估。整體而言，線性時變模型對於六級以上的地震，識別效果有限，若能以非線性時變模型模擬，應該更能幫助我們了解強震行為。振動台試驗因各層間距較小，系統呈現不穩定的狀態，若能改善儀器間互相干擾的情況，將對模擬實際地震行為更有幫助。

　　The parametric system identification method has been used to construct soil layer models and compute average model parameters of the ground vibration monitoring data at ChingLiao and Lotung. However, from the laboratory tests, the results show that the dynamic properties of soil are not always constant. An important goal of this study is to verify the soil properties changing with time. Before analyzing the data set, it is segmented into time-variant and time-invariant parts by adaptive forgetting through multiple models method (AFMM). Soil properties are estimated by both time-variant and time-invariant parametric modeling methods showing changes of system parameters. Besides, the shaking table test data is analyzed by using the parametric system identification.
　　The results of this study show that the AFMM can reduce the error of estimation for time-variant model and has advantages of sorting data set in analysis. The modal frequencies decrease during main shaking area after a certain threshold strain and they are relevant to earthquake intensity. Damping ratios might be underestimated without segmentation while modal frequencies might be overestimated. The results show that there is a limit for linear time-variant models to identify earthquakes above seismic intensity 6. If non-linear time-variant models can be used to simulate the strong ground motion, the result would be more accurate. The data from shaking table test is unstable, it may be due to small intervals between layers interfere with instruments. If the interference can be reduced, the test system will be more helpful to simulate earthquake behavior.

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